It is common practice to hydraulically pressure test a joint of steel pipe to assess its integrity. For example this is done in manufacturing yards where piping, valves, vessels, instruments and the like are connected together into modular assemblies.
The pressure test is commonly conducted at high pressure (as much as 5,000 psi). So the assemblies closing the open ends of a joint undergoing testing need to be competent to remain in place and leak-proof.
One suitable tool for this purpose is disclosed in our PCT publication WO2011/106893 A1. In FIGS. 10-15 this publication shows:                an external front plate which functions to abut the end face of a pipe end to close its bore opening;        an external circumferential clamp assembly which tightens onto and frictionally engages or grips the outer surface of the pipe end and anchors the assembly in place;        threaded nut and bolt means extending between the plate and clamp for drawing the plate tightly against the pipe end face; and        annular seal means interposed between the plate and pipe end face for sealing their interface.        
While the '893 tool has proven commercially viable, there remains a need for an improved tool characterized by: a simpler structure; reduced installation time; minimal internal scoring of the pipe inner surface; concentrated gripping power; and sealing capability which increases as the pressure in the pipe increases.